The cornea is not only a major component of the optical human eye, by providing about 75% of the total dioptric serves a protective function against a possible hostile to perform normally its functions (refraction, transmission, cornea must actively maintain its transparency and integrity
Replacement of an injured and/or opaque cornea with materials has a long history of failure and even today its limited.
As an alternative, the transplantation of human homologous tissue is successful in less complex pathological conditions, keratocomus or corneal dystrophies. However, with gross cornea, particularly when the host tissue is deeply characteristics are altered, or secondary glaucoma is present, in conditions such as alkali burns, ocular pemphigoid, syndrome, trachoma and other conditions, the clear graft rate significantly. Graft rejection or late graft failure decrease chances of a successful transplantation. In addition, even in with organized eye banking systems, there is a chronic corneal tissue. In the developing countries, less than 1transplants are carried out due to lack of availability of technology. If an artificial cornea (keratoprosthesis) was available with simple means of fixation then millions more people worldwide might rehabilitation.
The material almost exclusively used for keratoprostheses poly(methyl methacrylate), henceforth designated as PMMA. recorded history, the success of various types of from PMMA is still limited, mainly because of complications due to at the interface between stromal tissue and peripheral such as erosive tissue necrosis (melting), leakage of aqueous epithelialization, infection, and extrusion of the implant.
Poly(2-hydroxyethyl methacrylate) hydrogel, PHEMA, was another prosthetic material which received interest ophthalmologists. Biocompatibility of PHEMA in the cornea is established, having been used as implant material for (intracorneal lenses), as well as for epikeratoplasty. To a PHEMA has also been proposed as a material for good results in the animal models.
For many years, attempts have been made to use polymers PMMA, PHEMA, or other materials for keratoprosthetic implants. attempts are well documented by the patent literature, for Pat. Nos. 2,517,523; 2,714,721; 2,754,520; 2,952,023; 3,454,966; 3,458,870; 3,945,054; 4,346,482; 4,402,579; 4,470,159; 4,586,925; 4,612,012; 4,624,669; 4,676,790; 4,693,715; 4,772,283; and 5,030,230, and in Ger. Pat. No. 2705234; Neth. 8501403; and Fr. Pat. No. 2,649,605. For general reviews covering the keratoprosthesis see: Day, R., Transactions of the American Ophthalmological Society, vol. 55, pp. 455-475 "Artificial corneal implants"; Stone Jr., W., Yasuda, H. and Refojo, M. F., "-year study of the plastic artificial cornea-basic principles", in The Congress, King Jr., J. H. and McTigue, J. W., eds., Butterworths, pp. 654-671; Polack, F. M., British Journal of 55, pp. 838-843 (1971), "Corneal optical Mannis, M. J. and Krachmer, J. H., Survey of Ophthalmology, vol. 25, pp. (1981), "Keratoplasty: A Historical Perspective"; Barron, B. A., "Prostokeratoplasty", in The Cornea, Kaufman, H. E., McDonald, M. B., Barron, Waltman, S. R., eds., Churchill Livingstone, New York, 787-803.
The postoperative complications of PMMA implants appear to caused by the lack of a firm bond between the remaining these implants. Prostheses have therefore been designed distinct parts, namely a central optic cylindrical zone surrounding skirt made of materials different from PMMA such ceramics, preserved biological tissue and various these modifications did not lower significantly the implant revealed in the above mentioned reviews. It therefore became biocompatibility alone is not sufficient to overcome the leakage and extrusion. Ideally, the peripheral material should into the host biological substrate by cellular invasion and interface between material and tissue.